1. Field of the Invention
The present invention relates to a magnetic head for use in a magnetic recording apparatus such as a magnetic disk apparatus and a method of manufacturing the magnetic head.
2. Description of the Related Art
The conventional magnetic disk apparatus (HDD) has a magnetic head, as shown in FIG. 20. In the magnetic head 1 shown in FIG. 20, an Al.sub.2 O.sub.3 /TiC substrate 2 constitutes a slider portion 3. An electromagnetic conversion element serving as a recording/reproducing element 5 is embedded inside an insulation layer made of a thin AlO.sub.x film 4 formed on a main surface side of the Al.sub.2 O.sub.3 /Ti substrate 2. A trailing section 6 is constituted of the thin AlO.sub.x film 4 and the recording/reproducing element 5. A leading end 5a of the recording/reproducing element 5 is positioned on a medium opposed face 7 at the trailing section side.
In the conventional magnetic disk apparatus, the slider portion 3 of the magnetic head 1 is afloat over a surface of the magnetic disk by a pressure generated by the viscosity of air which flows rotatably according to the high-speed rotation of the magnetic disk. At this time, the leading end 5a of the recording/reproducing element 5 positioned on the medium opposed face 7 is spaced at a constant interval from the magnetic disk. The medium opposed face 7 of the trailing section 6 as well as the slider portion 3 are flying above the magnetic disk as an Air Bearing Surface (ABS).
In the conventional magnetic disk apparatus, the magnetic head 1 and the magnetic disk are not in sliding contact with each other while the magnetic disk apparatus is in operation. Thus, basically, a problem that the magnetic head 1 and the magnetic disk are worn does not occur.
The magnetic disk apparatus is demanded to have an improved magnetic recording density. In order to comply with the demand, the present tendency is to shorten the wavelength of a recording signal. But the shortening of the wavelength of the recording wavelength causes the output of the recording/reproducing element 5 to be reduced. In order to compensate the reduction in the output of the recording/reproducing element 5, it is necessary to decrease the flying height of the magnetic head 1 to further reduce the magnetic spacing between the leading end 5a of the recording/reproducing element 5 and the magnetic disk. In a magnetic recording density of 1.about.2 Gbpsi (Gbits/inch.sup.2) currently adopted, the magnetic spacing between the magnetic head and the magnetic disk is 80.about.90 nm, whereas in a magnetic recording density of about 3 Gbpsi, it is necessary to reduce the magnetic spacing therebetween to 60.about.70 nm. In a magnetic recording density of as high as 10 Gbpsi, it is necessary to reduce the magnetic spacing therebetween to less than 30 nm.
In such a background, much efforts have been made to reduce the flying height of the magnetic head 1. The magnetic spacing between the leading end 5a of the recording/reproducing element 5 and the magnetic disk cannot be effectively reduced even though only the flying height of the head slider is reduced. That is, the magnetic spacing between the leading end 5a and the magnetic disk is determined by the total of the following elements (1) through (4):
(1) Thickness of protection film and lubricating layer at magnetic disk side PA0 (2) Flying height of head slider PA0 (3) Thickness of protection film of magnetic head PA0 (4) Dishing amount of leading end 5a from the substrate (Al.sub.2 O.sub.3 /TiC substrate 2 or thin AlO.sub.x film 4) of magnetic head.
Regarding the flying height of the head slider of item (2), as a result of efforts made so far, it is possible to allow the head slider to be closer and closer to the magnetic disk during the operation of the magnetic disk apparatus. Under these circumstances, regarding item (1), the thickness of protection film and lubricating layer at magnetic disk side cannot be minimized to zero because it is necessary to allow a stable rotation of the magnetic disk. Thus, item (4) is important. That is, it is important to reduce the dishing amount of the leading end 5a of the recording/reproducing element 5.
However, the medium opposed face (ABS) 7, of the magnetic head 1, on which the leading end 5a is positioned is abraded with diamond abrasive grain in its final process. Consequently, it necessarily occurs that the leading end 5a is dished more than the substrate of the magnetic head by 15.about.20 nm.
That is, the leading end 5a of the recording/reproducing element 5 is made of a metal material such as an Ni--Fe alloy, a Co magnetic alloy or the like each having a hardness lower than that of the Al.sub.2 O.sub.3 /TiC substrate 2 or that of the thin AlO.sub.x film 4 as the undercoat and overcoat of the recording/reproducing element 5. Therefore, the leading end 5a is necessarily abraded deeper than the Al.sub.2 O.sub.3 /TiC substrate 2 or the thin AlO.sub.x film 4 by 15.about.20 nm, based on the difference between the hardness of the Ni--Fe alloy or the Co magnetic alloy and that of the Al.sub.2 O.sub.3 /TiC substrate 2 or that of the thin AlO.sub.x film 4, when the medium opposed face 7 is finally processed by means of abrasion. FIG. 21 is a view for describing the dishing at the leading end 5a of the recording/reproducing element 5. That is, FIG. 21 is a sectional view taken along a line A-A' of FIG. 20. A reference character "D" of FIG. 21 indicates the dishing amount of the leading end 5a. As apparent from the foregoing description, there is a limit in the reduction of the magnetic spacing between the magnetic head 1 and the magnetic disk.
As described above, including the above-described problem of the dishing, there is a limit in the reduction of the flying height of the magnetic head 1. In order to solve the problem, there has been developed a magnetic disk apparatus of contact recording/reproducing system for recording and reproducing signals by contacting the leading end 5a of the recording/reproducing element 5 with the magnetic disk. In this type of magnetic disk apparatus, it is important to prevent the abrasion of the magnetic head and the magnetic disk, because the magnetic head is always in sliding contact with the magnetic disk during its operation. To this end, a method of minimizing the pressing load of the magnetic head against the magnetic disc is adopted. But it is very difficult to prevent the magnetic head from being worn because the same portion thereof slidably always contacts the magnetic disk.
The present tendency is to apply a magnetoresistance effect element having a high sensitivity to compensate the track width decrease-caused reduction in the reproducing output of the recording/reproducing element 5. In the magnetic disk apparatus (HDD) in which the magnetic head is flying above the magnetic disk by utilizing the ABS, basically, the problem that the magnetic head contacts the magnetic disk does not occur, as described above.
Actually, the leading end of the recording/reproducing element contacts the recording medium because of a projection (called glide height) formed on the recording medium. The projection of the recording medium contacts the magnetic head at a greater force as the magnetic head flies at a shorter distance from the magnetic disk. The contact between the leading end of the recording/reproducing element and the recording medium results in the rise of the temperature of a specific portion of the magnetoresistance effect film of the recording/reproducing element, thus causing the output level of a signal-reproducing voltage to fluctuate and the deterioration (called thermal asperity) of the output waveform of a reading signal. Consequently, an error occurs.
In addition, resistance change-measuring sense current (.about.5 mA) causes the temperature of the magnetoresistance effect element to rise by about 40.degree. C. Thus, under an environmental temperature of 80.degree. C., the temperature of the magnetoresistance effect element will rise to 120.about.130.degree. C. Such a temperature rise of the magnetoresistance effect element will cause interface diffusion of the magnetoresistance effect film to occur and the characteristic of a magnetic layer composing it to deteriorate with age.
As described above, with the improvement of the magnetic recording density, the adoption of the contact recording/reproducing system and the art of spacing the magnetic head at a shorter distance from the magnetic disk are investigated. In the conventional contact recording/reproducing system, the wear of the leading end of the recording/reproducing element and that of the thin AlO.sub.x film in the periphery thereof cannot be prevented. Thus, in order to put the contact recording/reproducing system into practical use, the improvement of the wear resistance of these portions is an important problem imposed on the contact recording/reproducing system. Further, in any of the above-described systems, the improvement of the output of the reproducing signal is prevented owing to the limit in the reduction of the magnetic spacing caused by the problem of the dishing of the leading end of the recording/reproducing element. Thus, the reduction in the large dishing amount of the leading end of the recording/reproducing element is demanded.
The magnetic head to which the magnetoresistance effect element is applied as the reproducing element has a problem that when the leading end of the recording/reproducing element and the recording medium contact each other, the temperature of the magnetoresistance effect film rises locally due to the projection formed on the surface of the recording medium. Therefore, there is a demand for the development of preventing the temperature rise of the magnetoresistance effect film to restrain the generation of the thermal asperity and the deterioration of the characteristic of magnetoresistance effect film.